System of control



R. E. HELLMUND.

SYSTEM OF CONTROL.

APPLICATION r1150 SEPT. 13. 1916.

1,318,753. Patented 0011 1111111.

Trolley 1 Trolley Fiq. I. F iq 2.

2o 5/ so '-.-Ground WITNESSES INVENTOR Rudolf 5. He! lmund.

' Systems of Control, of which ellegheny and State of UNITED STATESPATENT OFFICE.

R'U'BOLI' a. uni-mm, or swtssvnnrmsrnvma, cannon re warmcnom nmcmc ummmacrunmo comm, a eonronnnen or SYSTEM OF CONTROL.

Application filed September 18, 1916. Serial 110. 119,887.

To all whom it ma concern:

Be it known t t I, RUBOIJ' E. HELL- mn, subject of the German Emperor,and a resident of swissvale in the count of l ennsylvania, ve inventedanew and useful I'm rovement in e foilowing is a specification.

My invention relates to systems of control for electric-railway motorsand the like and especially to the automatic control of motors of thedirect-current type during regenerative operation.

In my co-pending application, Serial No. 44,443, filed August 9, 1915 isshown a renerative-control system of the above-mentioned characterwherein an auxiliary source of energy, such as a dynamotor or amotornerator set, is employed for exciting the old windings of themomentum-driven machines, the arrangement of parts being such that aninherent and automatic decrease of regenerative voltage is effected uponan incipient increase of the main current, where- "by a desirablenegative compoundin effect is rovided in the system, and are atively stale system of regeneration obtains.

However, under certain emergency conditions, such as the interruption ofsuppiycircuit volta by reason of the trolley leaving the supp y-circuitconductor or assing a section break, it has "been found t at theregenerated voltage instantaneously rises to a relatively high valuebecause of the abovementioned inherent regulatinglfeatnres of thesystem. Inasmuch as the exciting dyn-amotor or motor-generator set isconnected in parallel relation to the main machines, it follows thatsuch rise of volta e tends to efiect an increase in the speed 0the'auxiliary machines which, in turn, causes an increase of the mainfield-winding excitation and the regenerated voltage, and thus, thecycle continues until flash-over conditions are obtained in the motor ofthe motor-generator set or in the 'dynamotor in the course of a secondor so.

The object of my present invention is to provide a relatively simple andeffective means for obviating the above-mentioned.

of supply-circuit voltage, for the final purpose of decreasing the mainfield-winding excitation, whereby flash-over conditions are revented. yinvention may best be understood by reference to the accom anyingdrawings in which several systems or automatically accomplishing l theintended result in various ways are s own. Figure'l is a diagrammaticview of a system of control arra in accordance with my present inven onand Figs. 2, 3 and 4 are similar views oi modifications of thesystemshown in Fig. 1. Referring to Fig. I of the draw the system showncomprises suitable supp y-circuit conductors res actively marked Trolhayand Ground a main dynamo-elec- Patented Oct. 14, 1919.

trlc machine that is adapted for regenerative ,generator set or adyn-amotor having a pair of armature windings 2 and 3 that aremechanicallv connected in any suitable manner, as by a shaft 4; a relaydevice 5 of the motor type for overning purposes to be set forth; atrans ormer 6 that is adapted to be energized in accordance with themain-circuit current; and a line switch LS and a second switch 17 forconnecting the system to the respective supply-circnit conductors, saidswitches being governed by the relay device 5 and the transformer 6-,under predetermined conditions to bedescribed.

The driving armature winding-2 of the motorgenerator set i is providedwith a series-related field winding 7, while a field winding 8 for thedriven or generating auxiliary armature winding 3 13 connected in seriesrelation with the driv' armature and its field winding, 9. tr in detaillater. v

The relay device 5 may be of any familiar construction wherein anelectric mom! exerts torque in opposition to some fixed biasing means,such as a spring or weight. The device shown comprises an armaturewinding 9 that is adapted to be energized from the transformer 6 ashereinafter demribedand a fieid win'di 10 that is connected across thesupply c rcuit. The armature 9 may be mechanically connected, through ashaft 11 or otherwise to a drum 12 or other similar member, the entirerotatable body being biased to a certain position b reason of the actionof a weight 13, whic works in opposition to the normally developedtorque of the armature winding 9, as indicated by the correspondingarrows. In the normal position in question, a contact segment 14 of thedrum 12 is adapted to bridge a pair of stationary contact members thatare included in the energizing circuit for the actuating coil of theswitches LS and 17, as traced in detail later.

The transformer 6 comprises a primary winding 15, that is connected inseries-circuit relation with the armature Alyand a. secondary winding 16that is directly connected across the terminals of the relay armaturewinding 9.

The magnetizable core member (not shown) of the transformer 6 is adaptedto become relatively highly saturated when a comparatively low value ofre enerated current is flowing. Consequent y, it will be understood,that, under normal, that is, relatively small, variations of regeneratedcurrent orvoltage, the induced electromotive force in the secondarytransformer winding 16 is comparatively slight, but that, under theabove-mentioned emergency conditions of an interruption ofsupply-circuit voltage, the resultant sudden and material temporarydecrease of main-circuit current causes an appreciable electro-motiveforce to be induced in the secondary transformer windin 16, whereby therelay armature 9 is su ciently energized to overcome the opposition ofthe weight 13 and thus actuate the drum 12 to a position wherein thecontact segment 14 thereof becomes disengaged from the correspondingstationary contact members to thus efiect the opening of the line switchLS and also that of the switch 17 Inasmuch as the particular system ofmain-circuit connections, other than that it possesses the' inherenttendency to undesirably increase the regenerated voltage underconditions of supply-circuit voltage interruption, is immaterial to mypresent invention, I have not deemed it necessary to set forth, indetail, a complete system for efiecting the illustrated circuitconnections or for inauguratin regenerative operation. It will be unerstood that any suitable and well-known system for accom lishing suchresults ma be utilized, and t e illustrated systems wi 1 be describedonly inso far as is necessary to a thorough understanding of the presentinvention.

Assuming that regenerative operation has been begun, with the circuitconnections established as illustrated, the main circuit may be tracedas follows: from the trolley through conductors 20 and 21, the lineswitch LS, in its closed position, conductor 22, primary winding 15 ofthe transformer 6, conductor 23, main armature A1, conductor 24,junction-point 25, conductor 26, main-circuit resistor R1, a switchingdevice 27 which may be of any familiar type but which is hereconventionally shown as an arrow-head, conductor 28, closed switch 17and conductor 29 to the negative supplycircuit conductor Ground.

The main field-winding excitation circuit is established from thepositive terminal 30 of the auxiliary generating armature 3 throughconductor 31 switch 17 conductor 28, switching device 2%, main-circuitresistor R1, conductor 26, junction-point 25, main field winding F1, andconductor 32 ,to the negagzive terminal 33 of the armature windmg Anauxiliary circuit is completed from the positively energized conductor20 through conductor 34, auxiliary driving armature winding 2, fieldwinding 7 therefor conductor 35, field winding 8 for the auxiliarygenerating armature 3, and 0011- ductors 36 and 29 to ground. Thegenerator armature winding 3 is thus always initially energized in theproper direction by reason of the traversa driving-motor current through'the field winding 8.

The governin circuit for the line switch LS is complete from thepositively energized conductor 31, which is directly connected to theauxiliary enerating armature 3, through conductors 3 and 38, the contactsegment 14 of the relay device 5 in its normal or operative position,conductor 39, the actuating coil 40 for the line switch and conductor 41to the negative terminal 33 of the auxiliary generating armature 3. It

of the auxiliary will be understood that an auxiliary source of (marother than the armature winding 3 may e utilized for energizin theactuatin coil for the line switch, if esired.

he actuating coil 42 for the switch 17 is connected, in parallelrelation, to the line-switch actuating coil and thus is also governed bythe contact segment 14: of the relay device 5.

As stated above, during normal or relatively small variationsofregenerative conditions, the relay device 5 remains in the illustratedposition, since a relatively small torque is created in the armaturewinding 9. However, upon the interruption of supply-circuit voltage andthe cons uent instantaneous substantial cessation 0 regenerated current,the relatively rapid changes of flux conditions in the transformerprimary winding 15 causes a correspondingly large value of electromotiveforce to be induced in the secondary transformer winding 16, inaccordance with familiar principles, whereby the previously mentionedaction of the armature winding 9 to overcome the opposing action of thein number for the sake of simplicity and Fig. 3,

clearness, any desired number of switches may be controlled from thesame relay device 5, in a manner similar to that shown, for opening 1%any other desired circuits. It will be served that the openin of theline switch LS disconnects the auxi ia'ry motor armature 2 from the mainmachine but not from the trolley. Thus, upon an interruption ofsupply-circuit voltage, the generated voltage of the mam-machine is alsoremoved from the auxiliary armatures, which is referable though notnecessary: in gr example, the line switch is so located that the o eningthereof discon nects the main machine and the auxiliary 'motor armaturefrom the supply circuit but not from each other. v

Referrin now to Fig. 2, the system shown comprises lie supply-circuitconductors, the main dynamo-electric machine, the maincircuit resistorR1, the transformer 6, and the auxiliary armature. windings of themotor-generator set 1, as illustrated in Fig. 1, and, in addition, alow-current relay device 44 of the solenoid ty for governing a switch 45to remove the s o -circuit from a main field-winding-circuit resistor46, under predetermined conditions, is provided, and shunt fieldwindings 43 and 47 are adapted to energize the respectiveauxiliaryarmature windings 2 and 3 in lieu of the previousl set forth fieldwindings 7 and 8.

In t e system being discussed, the primary windin 15 of the transformer6 is connected m the ound lead of the system,

while the seminary windin 16 is connected in series relation with the sunt field winding 47 across the terminals of the auxiliary generatorarmature winding 3.

The relay device 44 is provided with an actuating coil 48 that isconnected in seriescircuit relation with the main armature A1, and witha plurality of auxil'a contact members 49 that are connecte in circuitwith the actuating coil 50 of the switch 45 when the relay device 44occupies its upper or energized sition.

Assuming t at regenerative o eration has been inaugurated in any suitale manner, the illustrated main circuit connections may be traced asfollows: 'from the trolley through conductors 20, conductor 51,actuating coil 48 for the relay device 44, conductor 52, main armatureA1, conductor 53, j uncti'onoint 54, conductor 55, main-circuitresistor1, switching device 27, conductors 56 and 57 and the primary winding 15of the transformer 6 to the negative conductor Ground.

The main field-windin circuit is completed from one termina of theauxiliary generating armature 3 through conductor 58, switching device27, main-circuit resistor R1, conductor 55, junction-point 54, mainfield winding F1, conductor 59 and normally short-circuited resistor 46to the opposite terminal of the auxiliary armature. 3.

A further circuit is completed from the positively energized conductor20, through conductor 60, t e parallel-related auxiliary motor armaturewinding 2 and shunt field winding 43, conductor 61, and the primarytransformer winding 15 to ground.

The energizin clrcuit for the switch 45 is established om one terminalof the auxiliary generating armature 3 through conductors 58 and 62,auxiliary contact members 49 of the relay device 44 in its upperposition, conductor 63, the actuating coil 50 of the switch andconductor 64 to the opposite terminal of the auxiliary armatime 3.

In the present s stem also, during normal regenerat ve con itions, byreason of the highly 'saturhted condition of the transformer coremember, the effect of the secondary transformer winding 16 isinsignificant and becomes effective only under the above-mentionedemergency conditiofis of an interruption of supply-circuit voltage, withthe resultant instantaneous cessation or materi-al decrease ofregenerated current.

In, such circumstances, the appreciable voltage induced in the secondarytransformer winding 16 opposes the voltage of the nerating armature 3,whereby the excitation of the shunt field winding 47 therefor which isconnected in series relation with the transformer secondary winding 16,is correspondingly reduced to accordingly decrease the voltage of theauxiliary armature 3 and of the main field winding F1 in a very shortinterval of time. Thus, the voltage of the regenerative system will beprevented froin suddenl rising to a dangerous value. Sebsequent y, thatis, as soon as the temporary effect of the transform r has diappeared,the regenerated voltage 111 tendto a in rise, but in the meantime, asu'fiicient interval has been obtained to insure that the low-currentrelay device 44 has dropped to its lower position, whereby the switch 45is opened to insert the resistor 46 in circuit with the main fieldwinding F1 and thus further reduce the voltage available for deliverythereto. Also, switches corresponding to the switches LS and 17 of Fig.1 and any other selected switches may be opened, as will be understood,provided that such operation is desired, although the resistor 46 may bechosen of a value suflicient to prevent the previously-mentioneddangerous voltage rises at all times, and then the switches in questionneed not be opened.

The c ening of the relay device 45 may be readi y adapted to performanother function, if so desired. Assume, for example, a fully automaticauxiliary governing system of a familiar type, wherein aplurahty ofswitches or the contact members of an equivalent drum controller areemployed to vary the main-machine-circuit connections or conditions, inaccordance with the action of the well-known limit switchyas full setforth in my co-pending plication, rial No. 122,373, filed Se in r 27,1916. In such a case, the 0 ing of the relay device to interruptauxiliary cirthe normal 0 eration of the system; t is, to render t elimit switch tempo; ily inoperative. Furthermore, as also set forth inthe co-pendin application ifn question, a time-limit relay evlce of anyamiliar type may be employed to open the machine circuits if the periodof supplycircuit-voltage interruption approaches a value where a suddenresum tion' of the voltage might cause injury to the system.

The system of Flg. 3 difi'ers from that shown in Fig. 2 only in that theshunt field windings 43 and 47 for the auxiliary armatures 2 and 3,respectively, have been replaced by the previously-described fieldwindings 7 and 8, and, in addition, the secondary transformer winding 16is connected in parallel relation to the field winding 8 for thearmature 3.

Under the assumed normal re enerative conditions, the main circuit of te system under consideration is completed from the trolley throughconductor 20, the closed line.

switch LS, conductor 65, actuating coil 48 forthe relay device 45,conductor 66, main armature A1, conductor67, junction oint 68,main-circuit resistor R1, switching evice 27, switch 17, conductors and71 and the primary transformer winding 15 to the negative supply-circuitconductor Ground.

he main field-windin circuit is established from one termina of theauxiliary enerating armature 3 through conductor 2, switch 17, switchingdevice 27, main-circuit resistor R1, junction-point 68,.main fieldwinding F1 and conductor 73 to the opposite terminal of the auxiliaryarmature 3.

A further circuit is completed from the positively-energized conductor65, through conductor 74, the auxiliary driving armature 2, fieldwinding 7 therefor and con- .normal drop,

ductor 75, where 'the circuit divides, one branch including conductor 76 and the field winding 8 for the auxiliary generator armature 3 and theother branch including conductor77, the secondary transformer winding 16and conductor 78, whence the circuit is completed through the plrimarytransformer winding 15 to groun The energizing circuit for the actuatingcoil of the line switch LS is'established from one terminal of theauxiliary generatin armature 3 through. conductors 2, 70 an 79,auxiliary contact members 49 of the relay device 45, in its upperposition, conductor 80, the actuating coil 40'of the line switch andconductor 41 to the opposite terminal of the auxiliary armature 3. Theactuating coil 42 of the switch 17 is connected in parallel relation tothe line-switch actuatiiig coil 40.

Dunn normal regenerative o oration, when refitively small variations 0current occur, the secondary transformer winding 16 has a negli ibleefi'ect upon the fiel winding 8 for t e auxiliary generator armature 3,for reasons previously set forth. However, a certain uantity of currentwill, of course, be normal y diverted through the secondary transformerwindinglfi, and the field winding 8 should be designed with this matterin view.

Upon interruption of supply-circuit voltage and the consequentinstantaneous and material decrease of regenerated current, theinductive eflr'ect of such rapid decrease of current will cause thebuilding up of a material voltage in the secondary transformer winding16 which will act in the same direction as the normal voltage dropacross the secondary transformer windin but, being considerably largerthan sue the induced voltage will tend to drive a current through thefield winding 8 for the auxiliary generator armature 3 in the oppositedirection to that normally taken, as indicated by the dotted arrows.

Thus, the differential action of the normal and temporary currents inthe field winding 8 will cause a correspondin reduction of theefi'ective excitation pro uced thereby, with the result that thegenerated voltage of the auxiliary generator armature 3and the excitincurrent of the main field winding F1 wi be accordirgly' reduced toprevent the above-mention flash-over conditions. As previously describedin connecscribed in connection with Fig. 1, and, in addition, a secondmain dynamo-electric machine having an armature A2 and field winding F2,which machine is connected in parallel relation with the other mainmachine; and a second regenerated current -excited field winding 82, forthe auxiliary generator armature 3, which is adapted to act cumulativelywith respect to the allied field winding 8 and which is bridged by aninduction coil 83, or similar device, provided with a greater number ofturns than the field winding 82, and having a suitable magnetizable coremember 84, for the usual purpose of increasing the inductive effect.

As is the case with the previously described transformer 6, theinductive coil 83 is adapted to have a highly saturated core member witha relatively small current traversing the coil.

Assuming that regenerative operation has been begun in any suitablemanner, with the various circuit connections as illustrated, the maincircuits may be set forth as follows: from the trolley through conductor85, where the circuit divides, one branch including conductor 86, mainarmature A1,

conductor 87, junction-point 88, main-circuit resistor R1, the switchingdevice 27 and conductor 89 to junction-point 90, and the other branchincluding conductors 91 and 92, main armature A2, conductor 93,junction-point 94, main -circuit resistor R2, switching device 95, whichcorresponds to the switching device 27, and conductor 96 to thejunction-point 90, whence a common circuit is completed throughconductors 97 and 98, the parallel-related auxiliary field winding 82and induction coil 83, and conductor 99 to ground.

.The main field-winding circuits are established from one terminal ofthe auxiliary generator armature 3, through conductors 100, 98 and 97 tothe junction-point 90, where the circuitdivides, one branch includingconductor 89, switch 27, main-circuit resistor R1, junction-point 88,main field winding F1 and conductor 102 to junction-point 103, and theother branch including conductor 96, switching device 95, maincircuitresistor R2, junction-point 94 and main field winding F2 to theunction-point 103, whence circuit is completed through a compensating orseries-related field winding 104 to the opposite terminal of theauxiliary generator armature 3.

An auxiliary circuit is completed from the positively-energizedconductor 91 through conductor 105, auxiliary driving armature 2 fieldwinding 7 therefor, conductor 106, field winding 8 for the auxiliaryarmature 3 and conductor 107 to ground.

The system under consideration, as well as the single-machine systemspreviously described, is provided with a negative com field winding bothtraverse t pound eflect by reason of the peculiar relation of themam-circuit resistors tothe remainder of the system; that is, upon anincipient increase of regenerated or main-armature current, the currenttraversing the corresponding main field windin is automatically andinherently reduc to cause the regenerated current to a in assume thenormal value, and the opposite action inherently takes place in theevent of an incipient decrease of'main-armature current. Such a systemis fully set forth and claimed in above-identified co-pendingapplication afi consequently, only a brief exposition thereo will begiven at the present time.

It will be observed that the regenerated current of either main armatureand the exciting current from the auxilia generator armature 3 for thecorresgondmg main e particular main-circuit resistor R1 or R2 in thesame direction, as indicated by the arrows. As a result, upon theabove-mentioned increase of main armature current, the consequentlyaugmented voltage drop across the resistor R1 or R2 inherently andautomatically decreases the'value of volta available for delivery to thecones 11 mg main field sponding re notion of the main armature currentis obtained.

In the present system, such negative compound eflect is, however,partially compensated for or opposed by the action of the combined fieldwindings 8 and 82 for the auxiliary generator armature 3, since theadditive or positively assistin effect of theregenerated-current-excited eld winding 82 tends to increase the voltagedelivered by the auxiliary armature 3 upon an increase of regeneratedcurrent and, conversely, tends to decrease such voltage upon a reductionof main-annature current. It will be understood that the relative valuesof the above-mentioned negative compound efl'ect and of the partiallycounteracting effect of the field windin 82 for the auxiliary armaturemay be c osen to suit the desired operating conditions by suitabledesign of arts P Thus, the negative com ound effect in question acts ata relative y rapid rate to prevent material changes of regeneratedcurrent during normal 0 eratlon, whereas, the counteracting effect 0 thefield winding 82 for the auxiliary armature 3 acts at a slower rate byreason of the inherent inductance of the auxiliary field-winding circuitwhich requires that an appreciable interval of time must ensue beforethe field windin properly adjusts itself to the new conditions.

During normal regenerative operation,

.82 and, in this the induction coil 83, 0 reason of its highl saturatedcore memlier 84., will roduce but little effect upon the field win ingway, merely acts similarly to a resistor.

However, upon the above-mentioned material decrease of regeneratedcurrent reason of the interruption of supply-circuit voltage, thedecrease of flux in the induction coil 83 and the parallel-related fieldwinding 82 will set up counter-electromotive forces In the respective,coils, the induction coil 83 having a eater number of turns than theauxiliary eld winding 82, whereby the voltage induced in the inductionGOIl overcomes that induced in the field winding and, consequently, thecurrent traversing the field winding or actually reverses it.

Thus, under the emergency conditions in question, the field excitationof the auxiliary armature 3 is reduced to such a degree and in such atime interval that the current field. winding is suftraversin the mainficiently ecreased to prevent the aboveflash-over condimentionedundesirable tions. Moreover, the combined action of the field winding 82and the induction coil 83 is practically instantaneous, or, in otherwords, the usual time element that is involved in the variation ofcurrent and flux in the field winding 82 is substantially eliminated.

The series-related fieldwin 104, for the auxiliary armature winding maybe of either the well-known conductive or the inductive type and theefiect thereof is to prevent the occurrence of undesirable inuctiveefiects field windings,

I do not wish as will be understood.

to be restricted to the specific circuit connections or arrangement ofparts herein set forth, as various mod1- fications thereof may beeifected without departing from the spirit and sco of my invention. Idesire, therefore, t at only such limitations shall be imposed as areindicated in the appended claims.

I claim as my invention: 1. In a system of regenerative control, thecombination with a supply circuit, and a momentum-driven dynamo-electricmachine adapted to be connected to the supply-circuit and having anarmature an .a field winding, of an auxiliary dynamo-electric machinefor energizing said field .winding, a transformer having its primarywinding connected in circuit with said momentumdriven machine and itssecondary winding connected in circuit with said auxiliary machine tooppose the normal effect of a load change upon the system.

2. n a system of control, the combination with a supply circuit, a maindynamoelectric machine adapted to be connected to by of sudden changeeither materiall reduces in the circuit of the main I the su ply circuitand having1 an armature and a cl win ,ofanauxi iary dynam electricmachine or energizing said field winding, and inductive means associatedwith said machines for governing the operation of the auxilia machineonly in case 0 current lectric machine to oppose the main-dynamothenormal effect of a load change upon the system.

3. In a system of control, the combination hine an with adynamo-electric mac armature and a field winding, a means for energizingsaid field windi of means inductively associated with sai dynamoelectricmachine for controlling said enerzing means only in case of rapid changein the flow of current through the dynamoelectric machine to oppose thenormal effect, of a load change upon the system. i

4. In a system of regenerative control, the combination with adynamo-electric machine, of means for imparti thereto a negative compo dharacteristic normal regenerative operation, and means for counteractingharacteristic' under predetennined a norrha conditions.

5. In a system of regenerative control, the combination with a supplycircuit and a dynamo-electric machine apted to be con: nected theretoand having an armature and a field winding, of auxilia exciting meansfor said-field winding a apted to act in conjunction with theregenerated current to impart a negative compound characteristic to themachine during normal regenerative operation, and means operated underconditions of so ply-circuit-voltage interruption for nullimg saidcharacteristic to a redetermined egree.

In a system of control, the combination with a supply circuit anda.dynamo-electric machine a apted for connection thereto, of relativelyrapidly-operative means for couns teractin machine-load variations, andrelatively s owly-operative means for opposing said first means underpredetermined conditions.

7. In a system of control, the combination with a sup ly circuit and a damo-electric apted forconnection thereto, of main-circuit means forrapidly and inherently counteractin mac inc-load varialiens, andrelatively s owly: operative means for nullify'ing the action of saidfirst means to a certain degree under predetermined supply-circuitconditions.

8. n a system of control, the combination with a sup ly circuit and adynamo-electric flow through nausea herentl and rapidly counteractivariations 0 mainarmature current, an indu tive means-associated withcertain of said auxiliar field windings for producing'a 'reiativ y slowcounteract" efiect upon said first means under conditions ofsupplycircuit-voltage interruption. 2o 10. In a system of regenerativecontrol, the combination with a supply circuit and amomentum-driven'dynamo-electric machine having an'arrnature and a fieldwinding, of a switching device for modifying circuit connections, arelay device for governing said switching device an auxiiiary drivenenerator armature or enersizing said fie d winding and said switchinevice, a shunt field winding for said auxi armature, and a transformerhaving its winding connected in circuit with armature and its secondarywindin circuit with the auxiliary the mam i connected fie d winding. ast 11, In a system of regenerative control, the combination with a supply,circuit and a momentum-driven dynamo-electric machine having anarmature and a field windin of a resistor in circu't "with said fieldwin g, 40 a switching device for normally short-circuiting said resistor"a relay device for verning said switching device, an auxiliartgeneratin armature for energizing said eld win mg and said switchin device, a field windin for said auxi iary armature, and a trans ormerhaving its primary winding connected in circuit with the main armatureand its secondary windin connected in circuit with the auxiliary fielwinding.

12. In a system of control, the combination with a supply circuit and adynamoelectric machine adapted for connection thereto, of means 0 eratedunder conditions 5|} of supply-circuit vo tage interruption by theinductive efl'ect of the current traversingvthe armature of said machinefor modi the excitation of the field winding 0 the armature and a fieldwinding, of

.negative compound normal regenerative operation, and means,

, itions by traversing a ing machine oppositely to the normal effect ofa load change.

13. In a system of control, the combination with a suppiy. circuit and adynamoelectric machine adapted for connection thereto and having anarmature and a field windin of an auxiliary source of ener for sen ingcurrent through said field win high the opposite direction from thecurrent traversing said armature windin and means operated underredetermin supply-circuit-voltage conditions by the inductive efiect ofthe current traversing said armaturewinding for modifying theenergization of said eld winding. 7

14. In a system of control, he combination with a supply circuit and adynamoelectric machine adapted for connection thereto and having anarmature and a field winding, of an auxiliary source of energy 1 forsaid field winding, and means operated under conditions ofsupply-circuit-volta interruption by the inductive efiect of t e machinearmature windin for modifying the energization of said fie d windingoppositely to the normal efl'ect ofa load change.

15. In a'system of control, the combination with a supply circuit and adynamoelectric machine adapted for connection thereto, of transformermeans energized in accordance with main-circuit current for modifyingthe normal machine excitation under conditions of suppl -circuit-voltageinterruption oppositely to t e normal eifect of a load change.

16. In a system of regenerative control, the combination with adynamo-electric machine, of means for imparti thereto a characteristicduring operative upon a change of load current flow in a certaindirection, for temporarily counteracting said characteristic.

17. In a system of control, the combination with a supply circuit and adynamoelectric machine, of means, 0 erated under redetermined abnormalsupp y-circuit conthe inductive efiect of the current quently modifyingthe machine-circuit connections.

. In testimony whereof subscribed my name this 1916.

I have hereunto 1st day of Sept,

RUDOLF n. HELLMUND.

certain machine winding, for 'preventinga predetermined rise of machinevoltage, and automatic means for subse-

